The present invention relates to a data transfer control device, electronic equipment, and a data transfer control method.
The universal serial bus (USB) standard 2.0 is expanding well in the marketplace, but an interface standard called the USB On-The-Go (OTG) has been settled upon by the USB Implementers Forum (USB-IF). The OTG standard (OTG 1.0) that has been derived as an extension of USB 2.0 holds out the possibility of bringing out new additional value to the USB interface, and it is expected that applications that make use of these characteristics will appear.
This OTG makes it possible to impart a host function to a peripheral (peripheral device) connected to a host (such as a personal computer) by existing USB. This makes it possible to transfer data between peripherals connected by USB, enabling direct connection between a digital camera and a printer, by way of example, so that an image from the digital camera can be printed. It is also possible to connect a digital camera or digital video camera to a storage device, to save data therein.
However, it is usual for a peripheral that is given the host function by OTG to have a limited-capability CPU (processing section) incorporated therein. The addition of the host function therefore places a heavy processing load on the CPU (firmware) of the peripheral, making processing complicated and raising further problems such as impeding other processes and increasing the design period of the device.
In particular, if the firmware (processing section) determines whether or not the packet transferred by the final transaction is a short packet, the processing load on the firmware will increase, making it difficult to transfer a series of packets automatically.
It has been determined that there are some devices that cannot recognize the final end of transfer data if the packet that is transferred in the final transaction is a packet of the maximum packet size.